This invention relates to the coiling of plastic pipe. In one aspect, this invention relates to a method for producing a coil containing two lengths of pipe which can be simultaneously unwound from the coil. In another aspect, this invention relates to an apparatus for simultaneously winding a first length of the pipe and a second length of the pipe into a coil.
For many applications it is necessary to have a loop of pipe typically comprising a first and second run of pipe connected by a u-fitting such that fluid can flow through the first run of pipe, through the u-fitting and into and through the second run of pipe. One such application is geothermal heat exchange.
Typically, geothermal heating and air conditioning systems, i.e., heat pump systems, utilize the ground as a heat source or heat sink. To accomplish this, the geothermal system requires a subterranean heat exchanger which is coupled to a compressor/expander system, i.e., a heat pump. The subterranean heat exchanger comprises a single underground conduit loop or preferably a series of interconnecting underground conduit loops which extend out underground from the heat pump and loop back to the heat pump.
Thus, in a single conduit loop system, as illustrated in FIG. 1, heat exchange fluid circulating through heat pump 2 moves through underground pipe 4, circulates through u-shaped pipe 6, moves up through underground pipe 8 and returns to heat pump 2. Underground pipes 4 and 8, along with u-shaped pipe 6, form the inground conduit system 3. Typically, underground pipes 4 and 8 will be straight, and installed substantially parallel to each other and have a vertical or slanted orientation, preferably a vertical orientation for ease of installation. During the heating cycle, the heat transfer fluid absorbs heat from the earth 12 as it circulates through the inground conduit system 3 and then returns to the heat pump where the heat pump compresses the warm heat transfer fluid to a higher temperature, extracts the heat from it, and distributes the heat extracted through conventional duct systems in the building 10.
During the cooling cycle, heat transfer fluid circulating through inground conduit system 3 ejects heat which is absorbed by the earth 12. The thus cooled heat transfer fluid then returns to heat pump 2 to pick up more heat removed from the building 10.
FIG. 1 illustrates an example of a geothermal heat pump system using a single vertical ground loop for simplicity. However, most systems use more than one vertical loop, usually one loop for each ton of air conditioning capacity is used. The multiple loops are fused in parallel to a header pipe carrying the heat transfer fluid to and from the building. Alternately, systems can be arranged to use a slanted inground conduit system rather than a vertical inground conduit system.
Installation of a conduit loop for an in-ground conduit system comprises drilling a borehole and inserting two runs of pipe into the borehole, with their downhole ends connected by a u-bend fitting, into the borehole. The installation of an inground conduit system such as described above is complicated by the necessity of dealing with two separate coils of pipe for each conduit loop and interconnecting the pipe with a u-bend fitting at the job site. It would, therefore, be advantageous if a double run of pipe was provided in a single pipe coil.